Chromatographic apparatus

ABSTRACT

A CHROMATOGRAPHIC COLUMN FOR THE SEPARATION OF COMPONENTS OF A MIXTURE COMPRISING A HOLLOW MEMBER; A MEANS FOR INTRODUCING A MIXTURE INTO AND WITHDRAWING COMPONENTS FROM SAID MEMBERS; MEANS FOR DETECTING COMPONENTS ISSUING FROM SAID MEMBER; SAID COLUMN BEING PROVIDED WITH A PARTITIONING AGENT COMPRISING A POLYMERIC MATERIAL BONDED TO AN INTERIOR SURFACE OF SAID MEMBER EITHER DIRECTLY OR THROUGH AN INTERMEDIATE FILM OR COUPLING AGENT. A PARTITION AGENT-FORMING POLYMERIZING MONOMER IS DEPOSITED WITHIN THE INTERIOR OF THE HOLLOW MEMBER AND POLYMERIZE IN SITU. COMMONOMERS MAY BE EMPLOYED, AND CHAIN-STOPPING AGENTS, AN ALKYL HALIDE CAN BE USED TO REGULATE THE CHAIN LENGTH.

April 30, R. J Go OD CHROMATO'GRAPHIC APPARATUS 2 Sheets-Sheet 1 .FiledAug. 25, 1972 F/GZ FIG. 4

FIG.

FIG. 5

A ril 30, 1974 R .,.OOD 3,808,125

CHROMATOGRAPHIC APPARATUS Filed Aug. 25, 1972 I 2 Sheets-Sheet 2 HEXANEHEPTANE PENTANE TIME n-HEPTANE n-HEXANE N n-PENTANE fi-QCTANE FIG. 5

United States Patent 3,808,125 CHROMATOGRAPHIC APPARATUS Robert J. Good,Grand Island, N.Y., assignor to Phillips Petroleum Company Filed Aug.25, 1972, Ser. No. 283,776 Int. Cl. B0111 15/08 US. Cl. 210-31 C 13Claims ABSTRACT OF THE DISCLOSURE A chromatographic column for theseparation of components of a mixture comprising a hollow member; ameans for introducing a mixture into and withdrawing components fromsaid member; means for detecting components issuing from said member;said column :being provided with a partitioning agent comprising apolymeric material bonded to an interior surface of said member eitherdirectly or through an intermediate film or coupling agent. A partitionagent-forming polymerizing monomer is deposited within the interior ofthe hollow member and fl ice has been coated with a thin film ofpartitioning liquid 'for which the liquid or gaseous constituents of thesample have anaffinity.

The separation columns generallyused in chromatw graphic analysis havebeen either a packed column or a capillary column, depending upon theparticular sample being analyzed and the amount thereof. As the namesuggests, packed columns contain packed into the column discreteparticles which can function as a stationary phase per se by virtue ofabsorbing surfaces thereof or'as a support for a stationary phasecomprising a thin film of partitioning liquid. Capillary columns aregenerally of a polymerized in situ. Comonomers may be employed, and

chain-stopping agents, an alkyl halide, can be used to regulate thechain length.

This invention relates to chromatographic analyzers. More particularly,the invention relates to novel separating columns used inchromatographic analyzers and to a method of preparing such columns. 7

Chromatographic analyzers are a widely used tool for the measurement andcontrol of chemical processes. As a process control device,chromatographic columns are usually divided into two distinct units-ananalyzer unit located quite near the process stream and a programmerunit that can be located where needed. The analyzer must obtain its ownsample, analyze it, and process the detector information into someuseful quantity. Depending on the intended use, this quantity is thendelivered to either recorder, controller, or computer means..Theinstrument must continue to repeat the same cycle, sometimes as often asonce each minute, for many uninterrupted months with the high degree ofreliability.

Briefly, analysis of a sample by the chromatographic technique involvesinjecting a smallsample into an appropriate fluid carrier stream. Thefluid carrier stream conveys the sample through a separation columnwhich contains a material for which each of the respective components ofthe sample mixture has its own unique affinity or retention time. Thedifference in the afiinity or retention time of the respectivecomponents causes the individual components of the sample to stay withinthe column for different lengths of time before emerging. The aflinityof most liquid and gaseous compounds for various materials is well knownand the order of emergence of the individual components of a samplemixture can be easily determined. As each component emerges from thecolumn, it is passed through a detector device which measures aparticular property of the respective component against a referenceproperty of the carrier fluid. The output of the detector isrepresentative of the amount of the particular component in the sample.A recording of the input of the detector for a particular samplegenerally results in "a multipeaked curve, wherein each peak mayrepresent one component of the sample, and from which the quantity orpercentage of each of the components can be ascertained by knownprocedures. a

The material causing the separation within thecolumn of the respectiveliquid or gaseous components of the sample is commonly called thestationary phase of the column. Separation is effected either becausethe stationary phase has absorbing surfaces or because the; surfacesmaller diameter than packed columns and are not packed with aparticulate separation material. Rather, such columns have the innersurface thereof coated with a separating liquid phase, with the columnwall functioning as the support for the separation or partitioningagent.

Generally, in both types of columns, the bonding forces between thepartitioning agent and the support column, whether it be the column wallor discrete particles, has been due to physical adsorption. Thisphysical bonding is relatively weak and can be overcome by thermalfluctuations in the system or by displacement by another chemicalspecies. Further, because the effects of the bonding forcesare noteasily controlled, a uniform and optimum thickness of the film isdiflicult to obtain. If too much of the partitioning agent is used, theresult may be an uneven film which adversely afiects column etliciency,or film in which the slow diffusion of the species that are to beseparated causes a loss of separating speed and inefficiency. If toolittle partitioning agent is used, the result maybe that column capacityand efliciency are too low for effective separations. Most serious, thepartitioning agent may migrate and the separating behavior of the columnwill then be unstable. i 'Itis' an'object of this invention to providenovel chromatographic columns. It is another object of this invention toprovide chromatographic columns wherein the partitioning agent comprisesa discrete polymeric film.'-It is another object of this invention toprovide anovel ,apparatus' for making chromatographic separations. Astill further object of this invention is to provide a me'thod formaking capillary and packed chromatographic columns. These and otherobjects, aspects an'd 'advantages will be apparent from the disclosureand the accompanying drawings.

- elfectively' inhibits migration of the stationary phase and affords'improved'separation of components by providing a continuous film, ofpartitioning agent oftcontrolled; .essentially'unifo 'm thickness.

, A particular feature of the present invention vision of a uniquepartitioning .agent. comprising apoly;

meric material which is at least-chemically bondedtQathc surfaces of thechromatographic column itself ;and also, to relatively inert supportmaterials when such materials are used. The polymericmaterials canbecopolymerized among themselves. and with the column surfaces and.support ,materials in :an intimately intermixed order to provide astable continuous film extending throughout; the column which is capableof attracting or having selective aflinitiesfor particular solidmaterials. y

Thus, according to this invention, there is provided in one embodiment anovel column having therein a partitioning agent formed from a lowmolecular weight compound having chemical groups or radicals which reactwith a selected support. In addition, one or more of the chemical groupsare polymerizable functional groups, thereby permitting in situpolymerization of the partitioning agent. In another embodiment, theselected partitioning agent is at least chemically bonded to a selectedcoupling agent, which is in turn at least chemically bonded to aselected column support. In this embodiment, the elfective partitioningphase is a polymeric material formed in situ from a low molecular weightcompound having two or more reactive groups or radicals'such that achemical bond is formed to the coupling agent, without interference withthe in situ polymerization. The partitioning agent may also be bound tothe coupling agent by chain entanglement, the type of bonding which cannormally be accomplished for polymers of unlike chemical compositiononly when one polymer is formed in situ from a solu tion of monomer inthe other polymer. The coupling agent in this embodiment is selectedwhich has at least one group or radical which will bond chemically tothe selected support, and at least one group to which the partitioningphase will form a chemical bond; the coupling agent may also polymerizein situ, provided it does not lose the capability of chemically bondingto or chain entanglement with the partitioning phase. This invention isfully applicable to both liquid and gas chromatography.

The present invention provides chromatographic columns having severaldistinct advantages over prior art columns wherein the bonding betweenthe partitioning agent and support is by physical means. For example, bycontrolling the extent of the in situ polymerization, the optimumeflective thickness of the partitioning agent film can be obtained.Also, because of increased strength afforded by the chemical bond, thestability of the column is greatly increased. Furthermore, since thebonding to the support is effected through chemical reaction, theprobabilities of leaving exposed adsorption sites is reduced. Inaddition, migration of the stationary phase is inhibited.

The present invention provides a chromatographic column having a stable,uniform film of a polymeric stationary phase chemically bonded to thecoumn and/or support material when used; as well as a method forpreparing such columns by the in situ polymerization of the stationaryphase. The polymeric stationary phase may be thermoplastic (i.e., alinear or branched polymer) or it may be crosslinked. If the latter, itshall be crossinked only to such an extent that the compounds that areto be separated have appreciable solubility in the polymer. The degreeof crosslinking may be, in itself, a major contributor to theselectivity of absorption by the stationary phase.

The invention is particularly useful in capillary-type columns such asthose disclosed in US. Pat. 2,920,478.

Such columns generally comprisea circular tube or hollow member ofextended length having an internal diameter approaching capillarydimensions. The hollow member will generally have an internal diameterof from 0.001 to 0.003 inch and a length which can be on the order of100 to 500 feet. The dimensions per se are not critical, althoughextreme lengths require that the column be coiled in order to fit into atemperature bath and the small diameter does require care in handling.In such capillary columns, the stationary phase can be directly bondedto the interior wall of the hollow member comprising the chromatographicseparation column. Alternatively, the column can be first coated with acoupling agent which is capable of bonding chemically through valencebonds to the interior wall of the column. This finite film of couplingagent is overcoated with certain polymerizable monomers. Thepolymerizable monomer is polymerized in an t? a P y eric r ea? Wh te msthe p itio g agent and which is interlocked with the coupling agent byat least a chemical bond through valence bonds. The coupling agents,when used, can be monomeric or polymeric in nature.

Thus, the present invention provides chromatographic columns having, asthe stationary phase or partitioning agent, a continuous discretepolymeric material of an essentially uniform finite thickness integrallybonded chemically through valence bonds to the interior wall or surfaceof the column and/ or other support material, when used. The inventionfurther provides columns wherein the polymeric partitioning agent isbonded to the surfaces of the column or other support through a couplingmaterial or agent, which itself may be either a monomeric or polymericphase. 'In this latter embodiment, the coupling agent is directly bondedto the column wall or other support chemically through valence bonds andis bonded to the polymeric partitioning agent chemically through valencebonds, physically as by chain entanglement, or by a combination ofphysical and chemical bonding forces.

It is a feature of the present invention that the chromatographic columnmember per so be constructed of a rigid material having reactive groupson the surface exposed to the column interior, such as surface hydroxylgroups, and which is otherwise nonreactive with a polymeric partitioningagent and/or coupling agent. Suitable materials of construction for suchcolumns which possess the requisite attributes include glass, quartz,steel and metals such as aluminum, iron, copper, tin, titanium,chromium, nickel and the like, whose surface contains hydrated metaloxide group which provide the requisite surface hydroxyl groups; thesteel being presently preferred as a material of construction. Forpacked columns, any of the support materials commonly employed assupport packing can be used in the practice of the invention, providingthat such support materials have reactive groups on the surfaces thereofand are otherwise nonreactive with the polymeric partitioning agent and/or coupling agent.

The polymeric materials applicable as partitioning agents in thepractice of the invention can be broadly described as any addition orcondensation polymer having terminal end groups capable of reacting withthe surface hydroxyl groups of the column in their wall to effect achemical bonding through valence forces through the polymeric stationaryphase and the column wall; or which are capable of reacting withreactive groups of the coupling agent when used, to effect at least achemical bonding through valence forces between the polymeric stationaryphase and the coupling agent; it being understood that there is presentin such cases at least some physical bonding as by chain entanglement ofthe individual polymeric segments. In certain cases, the bonding betweenthe polymeric stationary phase and the coupling agent will be entirelyphysical, as by chain entanglement, i.e., in the case wherein thecoupling agent is also a polymeric material which is not copolymerizablewith the stationary phase or partitioning agent. In this instance, thesolution comprising the monomeric partitioning agent and monomericcoupling agent is deposited upon the column wall; the coupling agent ispolymerized in situ to leave the monomeric stationary phase dispersedthroughout the polymeric coupling agent; the coupling agent is thencoated with partitioning agent-forming polymerizable monomer; and thepartitioning agent-forming polymerizable monomer is polymerized in situ,including the monomer dispersed throughout the polymeric coupling agent.Thus, since no reaction occurred between the monomer phases of thecoupling agent and the partitioning agent, and no reaction occurredbetween the polymeric phase of the coupling agent and the polymericphase of the stationary agent, the bonding between the polymeric phasesis entirely physical in nature.

Polymeric materials which can be utilized as the part io s agent n the pice at h P sent i vention ins elude homopolymers and copolymers ofmonomers having a structure:

wherein each R can be the same or diiferent and each is individuallyselected from the group consisting of hydro gen, halogen, furyl,pyridinyl, carbazoyl, aryl, alkyl, alkaryl, cycloalkyl, aryl, alkaryl,alkenyl, alkynyl, halogen-substituted aryl, halogen-substituted alkaryl,halogensubstituted alkenyl, halogen-substituted alkynyl,halogensubstituted alkyl, halogen-substituted aralkyl,halogen-substituted cycloal-kyl, alkoxy-substituted aryl,alkoxy-substituted alkaryl, alkoxy-substituted alkenyl,alkoxy-substituted alkynyl, alkoxy-substituted alkyl, alkoxy-substitutedcycloalkyl, alkenylaryl, -COOR CONR CEN, -COR OR and R COO, wherein R isselected from the group consisting of hydrogen, alkyl, aryl, alkyl andaralkyl, the number of carbon atoms in each R, R or R being not morethan 21. Some examples of monomers which can be polymerized alone orcopolymerized together to form a polymeric partitioning agent inaccordance with the invention include the olefins such as ethylene,propylene, l-butene, l-pentene, 4-methyl-1-pentene, l-pentene, 1-octene, l-decene, 3-phenylpropene-1, vinylcyclohexane, and the like;conjugated dienes such as butadiene (1,3- butadiene),2,3-dimethyl-1,3-butadiene, isoprene, piperylene, 2-aryl-l,3-butadiene,2-methoxy-1,2-butadiene, and the like; haloprenes such as chloroprene(2-chloro1,3- butadiene), bromoprene, 2-epoxy-l,3-butadiene,methylchloroprene (2-chloro 2 methyl-1,3-butadiene),and the like;aryl-substituted olefins such as styrene; various alkyl styrenes such aso-ethylstyrene, n-tetradecylstyrene, and the like; p-chlorostyrene,p-bromostyrene, m-methoxy-pisopropylstyrene, o-chloro-p-decylstyrene,3-bromo-4 vi- 'nylbutene-1, p-methoxystyrene, alpha-methylstyrene, vinylnaphthalene, 4-butoXy-5-vinylpentyne-l, and the like; acrylic andsubstituted acrylic acids and their esters, nitriles and their amidessuch as acrylic acid, methacrylic acid, methacrylate, ethacrylate,methyl-alpha-chloroacrylate, methylmetacrylate, ethylmethacrylate,butylmethacrylate, methylethacrylate, heptadecylmethacrylate,phenylacrylate, o tolylmethacrylate, benzylethacrylate, acrylonitrile,methacrylonitrile, methacrylamide, N,N-diphenylacrylamide,N,N-di-o-tolylacrylamide; methylisopropyl ketone, methylisopropanylketone, methylvinylether, l-naphthylvinyl ketone, methylvinylether,2-anthrovinylether, vinyl alcohol, vinyl ether, vinyl chloride, vinylidene chloride, vinyl furan, vinyl pyridine, vinyl carbazole, vinylacetylene, and other unsaturated hydrocarbons, esters, alcohols, acids,ethers, etc., of the types described.

The present invention further provides processes for the manufacture ofchromatographic separating columns comprising a hollow member having aninterior wall, said interior wall having integrally bonded directlythereto, as by chemical means through valence bonds, a partitioningagent comprising a thermoplastic polymeric material or indirectlythereto through an intermediate monomeric or polymeric tfilm, whereinthe said intermediate film is bonded to said interior wall as bychemical means through valence bonds and to said thermoplastic polymericpartitioning agent as by chemical means through valence bonds, physicalinterlocking, or a combination of physical and chemical means.

Broadly, the chromatographic columns of this invention are prepared by aprocess comprising coating the interior wall of the chromatographiccolumn with a monomer solution and thereafter polymerizing said monomersolution in situ. In addition to forming a thermoplastic polymericpartitioning agent, the polymerization reaction effects bonding of thepolymeric partitioning agent to said interior wall.

In FIG. 1, there is illustrated a first embodiment of the inventioncomprising a chromatographic column wherein the partitioning agent isdirectly bonded chemically to the interior wall of the column. In thisembodiment, chromatographic column 10 comprises a hollow member 11having an interior wall 12, a partitioning agent 13 bonded to theinterior wall 12, and an axially extending opening 15 extending throughthe column 10. In practice, an inert carrier, such as gaseous helium ornitrogen, conveys a sample to be analyzed through the opening 15 andthereby provides a mobile phase for the chromatographic analysis. Thepartitioning agent 13 selectively absorbs or adsorbs the components ofthe samples, thereby acting as a stationary phase. Such a system can bedescribed as the elution-partition technique. It is important that theinternal wall 12 of hollow member 11 be covered with partitioning agent13 and that the thickness thereof be as uniform as possible.

In FIG. 2, there is illustrated a second embodiment of the inventioncomprising a chromatographic column wherein the partitioning agent isindirectly bonded through an intermediate film or coupling agent to theinterior wall of the column at least by chemical means. In thisembodiment, the coupling agent 14 is chemically bonded to wall 12 ofhollow member 11 and chemically, physically or by a combination ofchemical and physical means to partitioning agent 13.

In FIG. 3, there is illustrated a third embodiment of the inventionwherein the embodiment of FIG. 1 has been adapted for use in a packedcolumn. In this embodiment, chromatographic column 20 comprises a hollowmember 21 having an internal Wall 22, discrete particulate packingmaterial 23 dispersed within the interior of hollow member 21, andpartitioning agent 24. In this embodiment, partitioning agent 24 isdirectly bonded to both interior wall 22 of hollow member 21 and packingmaterial 23 by chemical means. The packing material 23 provides, incombination with wall 22, support for the partitioning agent 24 and alsoprovides contact area for the partitioning agent. In the packed columns,the carrier gas, in conveying the samples through the system, passesthrough the interstices of the porous medium provided by the packedcolumn. Consequently, the loading, which refers to the amount of thestationary phase in this system, is critical. Too much partitioningalgent collects in pools between the particles resulting in decreasedetficiency in the column. On the other hand, if too little partitioningagent is used, the optimum capacity of the column is not obtained; andthere may even be absorbing sites exposed which is detrimental to thecolumn operation. The size of the particles will depend upon thepressure drop permissible in the system. For As-inch diameter columns,100420 or -100 mesh particle size is preferred; for 4-inch diametercolumns, 40-6O or 60-80 mesh particle size is preferred. The meshnumbers refer to standard ASTM screens.

In FIG. 4, there is illustrated a fourth embodiment of the inventionwherein the embodiment of FIG. 2 has been adapted for use in a packedcolumn in a manner akin to the embodiment of FIG. 3. In this case,partitioning agent 24 is directly bonded to packing material 23 bychemical means and to the intermediate film, i.e., coupling agent, 25 byphysical means, chemical means, or a combination of such means,depending upon the nature of coupling agent 25. Coupling agent 25 is inturn directly bonded as by chemical means to the wall 22 of hollowmember 21.

In FIGS. 5 and 6, there are illustrated other embodiment of theinvention wherein the previously described embodiments have been adaptedfor use in packed columns. In the embodiment shown in FIG. 5,partitioning agent 24 is bonded to coupling agent 26 by chemical meansphysical means or a combination of such means, depending on the natureof the coupling agent and to wall 22 of hollow member 21 bychemicalmeans. Coupling agent 26 is in turn directly bonded as by chemical meansto packing material 23. In the embodiment shown in FIG. 6, thepartitioning agent 24 is bonded to coupling agents 25 and 26 in the samemanner as the bonding described in FIG. and coupling agents 25 and 26are directly bonded as by chemical means to packing material 23 at wall22 of hollow member 21, respectively.

FIG. 7 is a reproduction of a representative strip chart recording inwhich the partitioning agent was poly(vinyl stearate) bonded to thecolumn wall through vinyl triethoxysilane coupling agent.

FIG. 8 is a reproduction of a representative strip chart recording inwhich the partitioning agent was a polymer made from dimethyldiethoxysilane grafted to the column wall with vinyl trimethoxysilane.

In a broad sense, the novel chromatographic columns of this inventionare prepared by a process comprising depositing a partitionagent-forming polymerizable monomer, either as a liquid, from solutionor from the vapor state, within the interior of the column andthereafter polymerizing said monomer in situ, whereby the polymericpartitioning agent is anchored in place.

The novel chromatographic columns of this invention contemplate thechemical reaction of at least two materials. For example, in the firstembodiment, i.e., FIG. 1, there is contemplated a chemical reactionbetween the partitioning agent 13 and the interior Wall 12 of column 10.In the embodiment of FIG. 2, there is contemplated a chemical reactionbetween wall 12 of column and the coupling agent 14. As noted earlier,under at least some conditions, there can be a chemical reaction betweenthe coupling agent 14 and the partitioning agent 13. In the embodimentswhich illustrate packed columns, FIGS. 4-6, there is contemplated achemical reaction between the particulate packing material 23 and thepartitioning agent 24 and a chemical reaction between the partitioningagent 24 and the column wall 22, if no coupling agent is used. Thus, itis evident that the column wall material must be capable of chemicalinteraction with the partitioning agent or, if used, the coupling agent;and the particulate packing material, when used, must be capable ofchemical interaction with the partitioning agent or, if used, thecoupling agent. The coupling agents, when used, must not only be capableof chemical interaction between the column wall and particulate packingmaterial but must also be capable of either or both chemical reactionand physical interlocking with the partitioning agent.

In view of the similarities between the capillary columns and the packedcolumns, the materials useful for one column are also useful for theother column. For example, a partitioning agent which can be used in acapillary column can also be used in a packed column; a coupling agentuseful in a capillary column can be used in a packed column; and, in thecase of a packed column, a coupling agent capable of reacting with thecolumn Wall can also be used as the coupling agent between theparticulate packing material and the partitioning agent providing thatthe reactive sites of the column wall and the packing material arechemically reactive with the coupling agent. In addition to thesimilarity between the materials useful for both the packed andcapillary columns, the method for preparing the packed column is similarto that used for the capillary column embodiments.

The interior wall 12 or 22 of the chromatographic columns of thisinvention can comprise any material that is capable of entering into achemical reaction with the partitioning agent or coupling agent, whenused. Particularly preferred are such materials having exposed surfacehydroxyl groups. Such materials include glass, steel, aluminum,chromium, tin, nickel, and the like, with steel being presentlypreferred. In a like manner, the particulate packing material of thepacked columns comprises any material that is capable of entering into achemical reaction with the partitioning agent or coupling agent, whenused, through chemically reactive sites such as surface hydroxyl groups.Representative of suitable packing materials are diatomaceous earth,fire brick, silica, and the like. The intermediate film or couplingagent provides a means for chemical coupling or bonding the partitioningagent to the column wall or particulate packing material. Thus, thecoupling agent must be a material which is capable of entering into achemical reaction with the column wall or the particulate packingmaterial, when used. In addition, the coupling agent must be capable ofchemically interacting with the partitioning agent, or physicallyinterlocking with the partitioning agents such as by chain entanglement,or a combination of chemically interacting with chain entanglement.Thus, coupling agents which are suitable for use in the practice of theinvention must have a reactive group capable of chemically reacting withthe reactive site provided by the column wall or the packing material,and, in order to chemically react with the partitioning agent, must havea polymerizable functional group, or a group upon which polymerizationcan be initiated, such as vinyl, vinylidene, amino, conjugated diene,and the like. The polymerizable functional group copolymerizes with thepartitioning agent-forming monomer, or graft polymerization is initiatedin the group, to form the initial bond between the coupling agent andthe partitioning agent. Thus, in one embodiment, where the column wallcontains surface hydroxyl groups, the formula representative of thecoupling agent can be as follows:

wherein w, y and x are integers varying from 1 to 3 and where their sumequals 4; Z is halogen or a (R'-O) group, R being an alkyl, cycloalkylor aryl hydrocarbon radical or combination thereof containing from 1 to18 carbon atoms which may or may not contain substituent groups such ashalogen, ester groups, etc.; R is a group which contains a polymerizablefunctional group such as vinyl, vinylidene, oxirane, amino, conjugateddiene, and the like; and R is any inert group, such as an alkyl,cycloalkyl, aryl, aralkyl group, or such groups substituted with inertgroups.

The partitioning agent can comprise any material that will chemicallybond to the column wall according to the first embodiment of thisinvention or chemically bond to the particulate packing materialaccording to the third embodiment of the invention. In addition, thepartitionig agent must be capable of forming an integral chemical orphysical bond or a combination of chemical and physical bonds, to thecoupling agent according to the second embodiment of this invention orthe embodiments of FIGS. 4-6.

By way of illustration, and not limitation, let it be assumed that thesurface walls contain surface hydroxyl groups and a coupling agent is tobe used according to the second embodiment of this invention. Thisillustration of the selected partitioning agent is to be polystyrene, apolymer having the general formula of:

The (Z) moiety, supra, which in this instance comprises CH CH O-, reactswith the surface hydroxyl of the wall and with adsorbed water moleculesaccording to relationships such as the following:

E20 CHFCHSKOCaHQ! H I CH2=CHSKOC2HO2 1120 on1. on CH2=CHS1(OR')2 moCHFCHS'KOR'): carton on" com. cm=onsuoml orn=ons1 orm or." orr=onton.=os1-o-s1 0c2rn) 2 CH2=CH'. When the styrene monomer is introducedinto the system, together with a polymerization catalyst such as aperoxide, the functional group CH -=CH- reacts therewith by reactionssuch as the following:

m can -oH-cm-oH-orn wherein R"'O- is a peroxy-free radical, and Y can beany of the silicone-containing groups listed in the previous set ofequations, which at this point chemically bonded to the solvent R". Itwill be readily apparent that other free radical polymerizationinitiators can be used in lieu of peroxy-free radicals. The ultimatefree radical equation is the start of a vinyl polymerization reactionyielding The conditions of reaction determines the value of n, whichdescribes the degree of polymerization and thickness of the film of thepartitioning agent.

10 Suitable combinations of coupling agents and partitioning agentsinclude the following:

bisphenol A and epichlorohydrin, cured in situ with an aliphatic oraromatic amine, or amide, or a carboxylic acid anhydride.

Poly (ethylene oxide).

Poly(allyl glycidyl ether).

Epoxy-polymer, such as that formed irom bisphenol A and epichlorohydrin,cured in situ with an aliphatic or aromatic amine, or amide, or acarboxylic acid anhydride.

Poly(ethylene oxide).

Poly (allyl glycidyl ether).

Epoxy polymer, such as that formed irom bisphenol A and epichlorohydrin,cured in situ with an aliphatic or aromatic amine, or amide, or acarhoxylic acid anhydride.

Dimethyldimethoxysilane. Diphenyldimethoxysilane. Di(cyanopropyl)dimethoxysilane.

Beta-(3. 4'epoxycyclohexyl)ethyltrhnethoxysilane.

Gamma-glycidoxypropyitrimethoxysilane.

Methyltriethoxysilane.

If a monomer with functionality larger than 2, e.g., divinylbenzene, isused, it must be in a small proportion with a monomer havingfunctionality 2, such as styrene, so that crosslinking will not occur tosuch an extent as to restrict solubility of compounds that are to beseparated too severely.

Chromatographic columns are prepared by the processes of this inventionby a process comprising coating the interior wall surface of thechromatographic column with a polymerizable partitioning agent-formingcompound, said compound being characterized by reactive groups capableof chemically bonding to said column wall under conditions conducive topolymerization of said compound; polymerizing said polymerizablepartitioning agentforming compound to a thermoplastic or lightlycrosslinked polymeric state; and removing the excess partitioning agent.The steps of coating, polymerizing and removal of excess partitioningagent can be repeated as often as necessary to obtain the desiredthickness of the partitioning agent.

Such processes comprise coating the interior wall surface of thechromatographic column with a coupling agent, said coupling agent beingcharacterized by having reactive groups capable of chemically reactingwith the column wall and a second set of reactive groups capable ofentering into a polymerization reaction; removing the excess couplingagent, overcoating said coupling agent coating with a polymerizablepartitioning agent-forming compound, said partitioning agent beingcharacterized by reactive groups capable of interpolymerizing with saidcoupling agent; polymerizing in situ said polymerizable partitioningagent, together with said coupling agent; and removing the excesspartitioning agent. The steps comprising coating the coupling agentcoating with a polymerizable partitioning agent-forming compound, insitu polymerization and excess removal of excess partitioning agent canbe repeated as often as necessary to obtain the desired thickness ofpartitioning agent.

In the formation of chromatographic columns containing a packingmaterial such as diatomaceous earth, the above-described processes aremodified as follows:

(1) The chromatographic column can be packed with the particulatepacking material prior to the introduction of the polymerizablepartitioning agent-forming compound into the interior volume of thecapillary column.

(2) The partitioning agent can be deposited onto the packingmaterial'and polymerized in situ prior to placing the packing mediumwithin the interior of the column. In this case, a coupling agent and/oradditional partitioning agent-forming material may then be introducedinto the column interior in order to effect bonding and subsequentanchorage in place of the partitioning agent. Various othermodifications will be readily apparent in view of this disclosure.

The initial coatingstep, i.e., the coating of the interior wall of thechromatographic column, can be performed by conventional methods such asare used for coating capillary columns which involves introducing asolution or vapor containing the polymerizable partitioning agentformingcompound, the coupling agent, or an admixture of coupling agent andpolymerizable partitioning agentforming compound, together with anynecessary catalyst or polymerization initiators, into the column andforcing it -by air pressure or inert gas pressure therethrough.

The process steps directed to the removal of excess partitioning agentor coupling agent can be performed by measures such as flushing thecolumn with a suitable solvent, by purging the system with an inert gasat room temperature or an elevated temperature, or such other methods asare readily avaliable to the art.

Those steps which involve polymerization or copolymerization can beperformed at conditions known in the art. For example, if the couplingagent is characterized by a polymerizable vinyl group and thepolymerizable partitioning agent-forming compound is a vinyl ester suchas vinyl acetate, a free radical generating compound such as an organicperoxide, e.g., benzoyl peroxide, can be employed to initiate thepolymerization in the presence of absence of an inert hydrocarbondiluent. Similarly, if the coupling agent characteristically contains anepoxy alkyl radical polymerizing unit and the polymerizablepartitionin-g agent-forming compound is an oxirane, a catalyst such as aLewis acid, e.g., boron trifiuoride or ferric chloride, or a Lewis basesuch as a tertiary amine, can be added to the oxirane and the treatedcolumn contacted with the mixture of oxirane and catalyst to effectgrafting. Other suitable catalysts includue primary amines and acidicanhydrides. The polymerization step can be conducted in the presence orabsence of an inert hydrocarbon diluent.

Known polymerization modifiers can be used to preventexcessivecrosslinking of the grafted polymers. If it is desired to provide alight crosslinking and thereby improve dimensional stability, a smallamount of difunctional monomer in admixture with monofunctional graftingmonomers, e.g., divinylbenzene and styrene, can be used. The degree ofpolymerization can be controlled by the residence time in the presenceof an initiator or catalyst at a given monomer concentration andtemperature. The thickness of the film can be controlled by the numberof successive repetitions of the process of coating with monomer andpolymerization of monomer. If the polymerization process is employed,the thickening of the film may take place either by chain extension orby the formation of new chains which are entangled on the molecularscale with the chains in the first coat. It should be observed at thispoint that the present invention offers a convenient method forcontrolling or increasing the effective thickness of a polymer film inthe column. Heretofore the thickness was controlled by the quantity ofliquid, of constant molecular weight, transported into the column.Generally speaking, the ultimate purging step, i.e., removal of excesspartitioning agent, will usually be accomplished by purging the columnat an elevated temperature with an inert gas. The temperature atwhichthe column, which had been prepared according to this invention,would then be employed and any separation process would be below theelevated temperature employed in the purging or conditioning step.

. 1-2 EXAMPLE I The interior surface of a 300-foot length of 0.001inchpentane, acetone, and methanol. A coupling agent solution wasprepared by mixing vinyl triethoxysilane, methanol, and water in thefollowing volume percents: 15 percent, 75 percent, 10 percent,respectively. A slug (3-4 ml.) of the solution was forced through thecolumn by pressurized helium to coat the interior surface of the columnwith the coupling agent soltuion. The column was then purged by flowinghelium therethrough for about 2 hours. A partitioning agent solution wasprepared by dissolving 5 grams of vinyl stearate and 0.06 gram of laurylperoxide in 25 ml. of chloroform. A slug (3-4 ml.) of the partitioningagent solution was forced through the column by pressurized helium. Thechloroform was evaporated by passing dry helium through the column at 60C., leaving a film of vinyl stearate thereon. The vinyl monomer waspolymerized in situ by passing dry helium through the column at C. for16 hours. Following the polymerization step, the column was purged of unanchored materials by passing dry helium through the column for 24 hoursat 250 C. The chromatographic column thus formed was found to be stableup to 210 C.

The column prepared according to the procedure set forth above was usedto analyze a mixture of normal alkanes having from 5-7 carbon atoms. Thechromatogram presented in FIG. 7 illustrates the effectiveness of thecolumn in separating the mixture into the indicated components.

EXAMPLE II The interior surface of a ISO-foot length of 0.001 inch(I.D.) stainless steel tubing was washed successively with pentane,methanol, and chloroform. The column was then purged by passingwater-saturated helium therethrough for 2 hours. The water-saturatedhelium hydrated the metal oxide surface forming surface hydroxyl groups.The following solution was prepared:

2.4 ml. of vinyl trimethoxysilane, 10 'ml. of dimethyl diethoxysilane(DMDES), and 12 ml. of methanol.

A slug (3-4 ml.) of the solution was forced through the column bypressurized dry helium coating the interior, wall thereof. The 'silanemonomers coating thecolumn wall were polymerized by passingwater-saturated helium through the column for 2 hours at roomtemperature, ca. 23 C.

The polymerization step was repeated by passing another slug composed ofequal amounts of DMDES and methanol through the column followed by2-hour treatment with water-saturated helium. This step was in accordwith the principles already noted, that the thickness of the stationaryphase (polymerized DMDES) can be increased by repeating thepolymerization step.

The chromatographic column prepared by the above procedure was used toanalyze a gas composed of n-octane, n-heptane, n-hexane, and n-pentane.As shown on the chromatograph presented in FIG. 8, the resolution of themixture into its components was excellent.

Reasonable variations and 'rnodifications are possible within the scopeof the disclosure, the drawingsand the appended claims.

I claim:

1. A chromatographic column comprising a hollow member;

a partitioning agent within the inner volume of said member comprising acontinuous film of a polymeric material integrally bonded to a couplingagent; and

a coupling agent, said coupling agent being disposed as an' essentiallycontinuous discrete film between said partitioning agent and said hollowmember, said coupling agent being integrally bonded at least chemicallythrough valence bonds to the inner surface of said hollow member andbonded to said partitioning agent by a bonding means selected from thegroup consisting of chemically bonding through valence bonds, physicalinterlocking, or a combination of chemical and physical means.

2. A chromatographic column according to claim 1 wherein said couplingagent is vinyl triethoxysilane and said partitioning agent is poly(vinylstearate).

3. A chromatographic column according to claim 1 wherein said couplingagent is vinyl triethoxysilane and said partitioning agent ispoly(dimethyl diethoxysilane).

4. A chromatographic column according to claim 1 further comprising:

a particulate support material disposed within the inner volume of saidhollow member;

wherein said partitioning agent is disposed within said inner volume ofsaid hollow member as a continuous layer upon the exposed surface ofsaid support material; and

wherein said partitioning agent is integrally bonded to the surface ofsaid particulate support material at least chemically through valencebonds.

5. An apparatus for the separation of a fluid stream into componentfractions comprising:

a hollow member;

a partitioning agent disposed within the inner volume of said hollowmember, said partitioning agent comprising a continuous discrete film ofa polymeric material, said polymeric material being integrally bonded toa coupling agent;

a coupling agent, said coupling agent being disposed as an essentiallycontinuous discrete film between said partitioning agent and said hollowmember, said coupling agent being integrally bonded at least chemicallythrough valence bonds to the inner surface of said hollow member and tosaid partitioning agent by a bonding means selected from the groupconsisting of chemically bonding through valence bonds, physicalinterlocking or a combination of chemical and physical means;

means to introduce a fluid stream into said hollow member for separationof at least one component fraction;

means to drive said fluid stream in a generally axial direction throughsaid hollow member; and

means to withdraw one or more component fractions from said hollowmember.

6. An apparatus according to claim 5 further comprising:

a particulate support material disposed within the inner volume of saidhollow member;

'wherein said partitioning agent is disposed within said inner volume ofsaid hollow member as a continuous layer upon the exposed surface ofsaid support material;

wherein said partitioning agent is integrally bonded to the surface ofsaid particulate support material at least chemically through valencebonds; and

wherein said coupling agent is integrally bonded to the inner surface ofsaid hollow member at least chemically through valence bonds and to saidpartitioning agent by at least one means selected fiom the groupconsisting of chemical bonding through valence bonds, physicalinterlocking or a combination of physical and chemical means.

7. An apparatus according to claim 6 wherein said coupling agent isvinyl triethoxysilane and said partitioning agent is poly(vinylstearate).

8. An apparatus according to claim 6 wherein said coupling agent isvinyl triethoxysilane and said partitioning agent is poly(dimethyldiethoxysilane).

9. A process for preparing a chromatographic column comprising:

coating the interior surface of a hollow member with a coupling agent,said coupling agent being characterized by the presence of reactivegroups capable of reacting with said interior surface and containingalso polymerizable reactive sites; thereafter coating said couplingagent-coated interior surface with a polymerizable monomer tosubstantially uniform finite thickness, said polymerizable monomer beingcharacterized by containing polymerizable groups; and polymerizing insitu said monomer to form an essentially continuous polymeric phase ofsubstantially uniform finite thickness, said polymeric phase beingintegrally bonded to said coupling agent by at least one means selectedfrom the group consisting of chemically bonding through valence bonds,physical interlocking or a combination of physical and chemical means.10. A process according to claim 9 wherein said coupling agent is vinyltriethoxysilane and said polymeric phase is p'oly( vinyl stearate) 11. Aprocess according to claim 9 comprising the steps of coating theinterior surface of a hollow member with a mixture of a coupling agentand a partitioning agentforming. polymerization monomer, to asubstantially uniform finite thickness,

said coupling agent being characterized by the presence of reactivegroups capable of reacting with said interior surface, said couplingagent further being capable of self-polymerization and copolymerizationwith said partitioning agent-forming monomer; said partitioningagent-forming polymerizable monomer being capable of reacting chemicallywith said interior surface, said polymerizable monomer further beingcapable of self-polymerization and copolymerization with said couplingagent, polymerizing in situ said mixture of coupling agent andpartitioning agent-forming polymerizable monomer to form an essentiallycontinuous first thermoplastic polymeric phase of substantially uniformfinite thickness, said first polymeric phase being integrally bonded atleast chemically through valence bonds to said interior surface of saidhollow member; coating said first polymeric phase with a partitioningagent-forming polymerizable monomer to a substantially uniform finitethickness; and

polymerizing in situ said polymerizable monomer to form an essentiallycontinuous second thermoplastic polymeric phase of substantially uniformfinite thickness, said second polymeric phase being bonded to said firstpolymeric phase by at least one means selected from the group consistingof chemical bonding through valence bonds, physical interlocking or acombination of physical and chemical means.

12. A process according to claim 11 wherein said coupling agent is vinyltriethoxysilane and said partitioning agent-forming polymerizablemonomer is dimethyl diethoxysilane.

13. A process according to claim 9 wherein the resulting couplingagent-coated surface is washed with an inert diluent to remove excesscoupling agent prior to the coating of said surface with saidpolymerizable monomer.

References Cited UNITED STATES PATENTS 3,514,925 6/1970 Bossart 553863,722,181 3/1973 Kirkland et a1 210-31 C 3,005,514 10/1961 Cole et a1.55386 3,116,161 12/1963 Purnell 55386 X 2,920,478 1/ 1960 Golay 5567 X3,663,263 5/1972 Bodre et a1 210-31 C JOHN ADEE, Primary Examiner U.S.Cl. X.R.

